Information systems enable information to be provided to recipients. For example drivers and road users may be warned against varying road conditions. The information such as the instantaneous speed limits, weather information, lane condition information, road dynamics and tunnel information, etc. may be provided via the system. With the advance of light technology, light emitting diodes (LED) have been widely used as the light source. With today's technology, the LEDs provide the light intensity of the conventional light sources by consuming much less energy. In addition, their small size, longer lifetime and inexpensiveness have enabled them to become preferred over the conventional light bulbs. As a result, the LED technology is preferred in order to enhance the optical performance and render images with smaller pixels in the information systems.
The information systems generally comprise an electronic circuit board on which the light source is mounted, the absorber front surface and the optical element, which enables the light source to attain the desired optical standards. The information systems have certain standards based on their radiation intensity, angle, colour and contrast ratio. These standards determine the range of visibility in which the system may be displayed and the quality of the vision.
Although it is possible to directly employ the LED in information systems, it is appropriate to use an optical element with protective and optical features in order to enable the LED being used to be less affected by the ambient conditions and to achieve the desired angle, colour, radiation and contrast values. In order to increase the contrast, it is necessary to reduce the back reflection of the sunlight with angles of incidence which are specified in standards. The information systems may suffer from back reflection of sun beams in the information system.
FIG. 1 depicts a side view of the information system according to the prior art. The information system comprises:
a light source 2 on an electronic circuit board 1;
an optical element OP comprising an optical axis to display information by directing light received at an entrance surface 5 from the light source 2 through the optical element OP to an exit surface 6 for the light to exit the optical element OP. The system is provided with a front surface 3 in which the optical element OP may be mounted.
EP0930600 discloses that the sunlight guided from the front surface of the lens may be absorbed by features in the optical element or the holder of the optical element.
EP1593109 discloses a sheet with a greater refractive index surrounding the lens whereby the sunlight beams guided onto the bottom surface of the lens are absorbed on the sheet surface due to the difference in the refractive indices.
Moreover, the position of the light source along with the lens must be precisely adjusted in three dimensions. According to patent no. EP1593109, the light sources are fastened to the surface of the lenses positioned on the front surface. Owing to this method, the light source is enabled to be precisely positioned in the lens in 3 dimensions. However, the need to separately screw each lens according to this method is both costly and slows down the production process.
EP1643473 discloses a bevelled lens portion in the optical element to direct the sunlight from the sun to a projection acting as an absorption screen in the optical element.
Changes made in the optical element to absorb reflections of sun beams however may disturb the desired radiation intensity, colour, or illumination angle that is provided by the information system. The optical element may have low illumination efficiency caused by the features for absorbance in the optical element.